1. Field of the Invention
The present invention relates to a substrate transfer technique for transferring a substrate between modules.
2. Description of Related Art
In a photolithography process as one of the semiconductor manufacturing processes, a resist pattern is formed by applying a resist to the surface of a semiconductor wafer (hereinafter referred to as “wafer”), by exposing the resist with a predetermined pattern, and by developing the exposed resist. Such a process is generally performed by using a system comprising a coating and developing apparatus configured to perform resist application and development and an exposure apparatus connected to the coating and developing apparatus.
The coating and developing apparatus includes resist coating modules each configured to apply a resist onto a wafer, and developing modules each configured to supply a developing solution to the wafer, and further includes heating modules each configured to heat a wafer before or after processed in the resist coating modules and the developing modules. Between the respective modules, and between the coating and developing apparatus and the exposure apparatus, wafers are transferred by substrate transfer units each provided with an arm.
An example of the conventional substrate transfer unit is briefly described with reference to FIG. 14. In FIG. 14, the reference number 101 depicts a guide; the reference number 102 depicts a frame capable of horizontal movement; the reference number 103 depicts an elevating table; and the reference number 104 depicts a rotating table. The reference number 105 depicts arms each for holding a wafer W capable of moving forward (advancing) and rearward (retracting) with respect to the rotating table 104. Thus, the substrate transfer unit 100 shown in FIG. 14 has a four-axis structure including moving mechanisms for linear motion along a horizontal motion axis (Y-axis), for linear motion along a vertical motion axis (Z-axis), for rotating motion about a rotational axis (θ-axis), and for linear motion along a substrate transfer axis (X-axis). The assembly comprising the frame 102, the elevating table 103, and the rotating table 104, which moves the arms 105 between the modules, is referred to as “moving part 110”.
In one example, modules 108 and 109 are located at different heights as shown in FIG. 14. When a wafer W is transferred between these modules 108 and 109, the frame 102, the elevating table 103, and the rotating table 104 are operated such that the arm 105 is positioned to face one of the modules in front of that module. Thereafter, the advancing motion of the arm 105 toward the module is started, and the wafer W is transferred between the module and the arm 105.
The frame 102, the elevating table 103, and the rotating table 104 may be operated in different time frames. They, however, are simultaneously operated in order to improve throughput. In the graph shown in FIG. 15, the abscissa axis indicates time passage; and arrows respectively indicate the motion periods of motion axes of the substrate transfer unit 100. FIGS. 16(a), 16(b), 16(c) and 16(d) respectively show transfer states of the wafer W at time points E1, E2, E3 and E4 in the graph. FIGS. 17(a), 17(b), 17(c) and 17(d) respectively show the position of the arm 105 with the rotating table 104 in the corresponding FIGS. 16(a), 16(b), 16(c) and 16(d). Herein, the movement of the moving part 110 from a position in front of the transfer-departure module 108 to a position in front of the transfer-destination module 109 is referred to as “intermodular travel”, and the advancing motion of the arm 105 is referred to as “substrate transfer motion”.
During the intermodular travel, if all axis motions are performed at their maximum speeds, the time required for Y-axis motion (i.e., horizontal motion of the frame 102) is longest. As shown by the dotted arrows in FIG. 15, the time required for the Z-axis motion (i.e., vertical motion of the elevating table 103) and the time required for the θ-axis motion (i.e., rotating motion of the rotating table 104) are shorter than the time required for the Y-axis motion. However, as described above, since the substrate transfer motion (X-axis motion) is performed after the completion of the intermodular travel, the motion speed of the Z-axis motion and the motion speed of the θ-axis motion need not set so high. Thus, the motion speeds of the Z-axis motion and the θ-axis motion are set lower than their highest possible speeds such that the Z-axis motion and the θ-axis motion are both finished at the time when the Y-axis motion is finished, i.e., concurrently with the elapse of time t1 from the start of the Y-axis motion. Thus, if the advancing motion (i.e., X-axis motion; substrate transfer motion of the arm 105) requires time t2, the time equivalent to the sum of time t1 and time t2 is required to complete the intermodular travel and the substrate transfer motion. However, further improvement in throughput is desired for the aforementioned coating and developing apparatus.